Many systems have been developed for controlling the extent to which food is heated and cooked in microwave ovens. These include aperture control to selectively heat different foods to different temperatures, such as found in Brown U.S. Pat. No. 3,219,460, Stevenson U.S. Pat. No. 3,547,661, Virnig U.S. Pat. No. 3,672,916, and Greenfield U.S. Pat. No. 4,080,524. Others use food-packaging materials directed to achieving cooking control by limiting the quantity of microwave radiation that can pass to the food. See, for example, Flautt U.S. Pat. No. 4,268,738. Others use microwave absorbent materials which heat when they receive radiation.
This prior work, however, is directed to controlling the quantity of microwave radiation, or resulting heat energy, to reach the food. It does not control the actual temperature reached by the package, and, so, the surface temperature reached by the food. My invention controls surface temperature plus total thermal energy, and does it by controlling the areas of, and surface resistivity of, discrete portions of metallized coatings formed on a dielectric film. This metallized coated film may be used to surround the food or as a surface upon which the food can rest. Accordingly, it serves to provide for surface cooking of food at a predetermined temperature.